( i need Unique answer, don't copy and paste, please)

Let N be an n-bit positive integer, and let a, b, c, and k be positive integers less than N. Assume that the multiplicative inverse (mod N) of a is a^(k-1) Give an O(n^3) algorithm for computing a^(b^c) mod N (i.e., a raised to the power b^c with the result taken mod N). Any solution that requires computing b^c is so inefficient that it will receive no credit.